1. Field of the Invention
This invention relates to a magnetoresistive effective type element, a method for fabricating the magnetoresistive effective type element, a thin film magnetic head including the magnetoresistive effective type element, a magnetic head device and a magnetic disk drive device which include the thin film magnetic head.
2. Related Art Statement
Information is recorded and stored in a magnetic recording medium by utilizing the direction of the magnetization thereof. With the development of high density recording for a magnetic recording medium, such an attempt is made as to narrow the track width of the magnetic recording medium and thus, to develop the longitudinal recording density thereof. In this point of view, a high sensitive reading head to read out information stored in the magnetic recording medium precisely is desired. As such a high sensitive reading head, recently, a thin film magnetic head having a magnetoresistive effective type element is utilized.
FIG. 31 is a perspective view showing a conventional magnetoresistive effective type element. In FIG. 31, a magnetoresistive effective type element 10a includes a base 1 made of AlTiC or the like, a base protective layer 2, a bottom shielding layer 3 and a bottom insulating layer 4 which are stacked on the base 1 in turn. Then, a magnetoresistive effective film 5 is formed on the bottom shielding layer 4, and magnetic biasing layers 6, 6 are formed so as to be adjacent to both sides 5b of the magnetoresistive effective film 5. Then, electrode layers 7a, 7a are formed on the magnetic biasing layers 6, 6 so as to be contacted with the edge portion 5c of the top surface 5a of the magnetoresistive effective film 5.
FIG. 32 is a perspective view showing another conventional magnetoresistive effective type element. In FIG. 32, like reference numerals are imparted to similar constituent elements to those of the magnetoresistive effective type element 10a illustrated in FIG. 31, and explanation for similar constituent elements is omitted. The magnetoresistive effective type element 10b is different from the magnetoresistive effective type element 10b in the contacting condition of the electrode layers. In the magnetoresistive effective type element 10b, the electrode layers 7b, 7b are formed on the magnetoresistive effective film 5 so as to cover the edge portion 5d of the top surface 5a of the magnetoresistive effective film 5.
FIG. 33 is a cross sectional view showing the magnetoresistive effective type element 10b illustrated in FIG. 32, taken on line X-X where the top surface 5a of the magnetoresistive effective film 5 is covered with the electrode film 7b and which is perpendicular to the top surface 5a and an air bearing surface (ABS) 11. In FIG. 33, an insulating film 12 is formed at the opposite side of the magnetoresistive effective film 5 to the ABS 11 so as to have substantially the same thickness as that of the film 5. The electrode layers 7b, 7b are formed on the edge portion 5d of the top surface 5a of the magnetoresistive effective film 5 and the insulating film 12. Not depicted in those figures, a top insulating layer and a top shielding layer are stacked in turn.
In the magnetoresistive effective type elements 10a and 10b illustrated in FIGS. 31 and 32, the magnetic biasing layers 6, 6 function as their respective magnetic domain-controlling films through the application of biasing magnetic field for their respective magnetoresistive effective films 5. Also, the electrode layers 7a and 7b function as their respective leading films to supply sense currents to their respective magnetoresistive effective films 5 from external power supply. When an external magnetic field is applied to the magnetoresistive film 5, the electric resistance thereof is changed. Therefore, a given sense current is supplied to the magnetoresistive effective film 5 from the electrode layers 7a or 7b, and thus, information magnetically recorded can be read out by detecting the change in sense current depending on to the magnetic direction.
In the magnetoresistive effective type element 10b, as shown in FIGS. 32 and 33, the electrode layers 7b, 7b are formed so as to cover only the edge portion 5d of the top surface 5a of the magnetoresistive effective film 5. In the application of sense current for the magnetoresistive effective film 5, a sense current 13b is applied directly to the magnetoresistive effective film 5 from the electrode layers 7b, 7b, and a sense current 13c is applied to the magnetoresistive effective film 5 from the electrode layers 7b, 7b via the magnetic biasing layers 6, 6. In the configuration as shown in FIGS. 32 and 33, the sense current can not be applied to the magnetoresistive effective film 5 sufficiently due to the large electric resistance. In addition, large amount of heat may be generated due to the large electric resistance when the sense current is applied.
In the magnetoresistive effective type element 10a, as shown in FIG. 31, the electrode layers 7a, 7a are formed so as only to be contacted with the edge portion 5c of the top surface 5a of the magnetoresistive effective film 5. Therefore, a given sense current 13a is applied to the magnetoresistive effective film 5 from the electrode film 7a via the magnetic biasing layers 6, 6. As a result, the sense current can not be applied to the magnetoresistive effective film 5 sufficiently, and large amount of heat may be generated due to the large electric resistance.
Moreover, in the magnetoresistive effective type elements 10a and 10b, the electric resistance between reading terminals is increased as the electric resistance of the magnetoresistive effective type element 10a or 10b is increased, so that the design margin of electric circuit to process information read including an amplifier may be reduced.